In SIP, there defines 3 types of DTMF: RFC2833, Inband, Info. You might doubt how to distinguish or check them.
We can check the DTMF directly in the VoIP Call Flow viewed by Wireshark. How to Analyze SIP Calls in Wireshark
Select the RFC2833 RTP event to check the details. It's pretty straight forward.
If you output the audio, the RFC2833 RTP doesn't have any sound.
It is the actual sound of the DTMF. If you play RTP steams in Wireshark, you can see the DTMF wave.
If need to check more wave details.
Firstly output the audio followed by this article: How to Output the SIP Call Audio for Wireshark Capture File
Then follow this article to check the DTMF wave: How to Check DTMF Wave?
It's a SIP packet. You can easily find out in the call flow view of Wirshark.
In the message body of the packet, you would see the digit information.